Radio communication system components, such as transmitters and receivers, include a variety of filters, modulators, mixers, and oscillators for processing both digital and analog signals. Many of these devices have resonators made from discrete circuit components, such as capacitors, inductors, and resistors. The limitations of discrete circuit components in resonators are well known. They exhibit non-ideal, unstable or parasitic behavior. They are also heavy and bulky, impeding light-weight and cost effective designs in radio circuits.
The piezoelectric properties of crystalline structures are also well known. Applying an electric field to a piezoelectric crystal will distort the crystal lattice. Similarly, mechanically deforming a piezoelectric crystal produces an electric field. Piezoelectric crystals also resonate at various frequencies, and they are often used as resonators in radio circuits.
Despite the valued properties of piezoelectric crystals, their use in radio circuits has been substantially limited to oscillators and filters, where they are well suited for introducing frequency stability. Nevertheless, it is a disadvantage that the resonant frequencies of a piezoelectric crystal are fixed at the time of manufacture and that its properties may degrade over time. While the use of crystal resonators has provided performance benefits, it has not reduced the use. of discrete devices in radio circuits, and the potential benefits of piezoelectric properties remains largely untapped.